Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/5/84; site othervax.UUCP Path: utzoo!watmath!clyde!cbosgd!ihnp4!qantel!lll-crg!seismo!cmcl2!philabs!micomvax!othervax!ray From: ray@othervax.UUCP (Raymond D. Dunn) Newsgroups: net.consumers Subject: Re: Radio Shaft vs GE NiCads Message-ID: <730@othervax.UUCP> Date: Thu, 28-Nov-85 11:44:41 EST Article-I.D.: othervax.730 Posted: Thu Nov 28 11:44:41 1985 Date-Received: Sat, 30-Nov-85 01:06:45 EST References: <6871@amdcad.UUCP> Reply-To: ray@othervax.UUCP (Raymond D. Dunn) Organization: Philips Information Systems - St. Laurent P.Q., Canada Lines: 90 Keywords: Ni-Cad,technical,boring,yawn Summary: Everything you never wanted to Know about Ni-Cads In article <6871@amdcad.UUCP> phil@amdcad.UUCP (Phil Ngai) writes: >It seems that Radio Shack sells AA NiCads for about $2 each while GE >sells them for twice as much, about $4 each. They are both the same >size, AA, same voltage, 1.2 V, and the same capacity, about 450 mA-Hr. >(the capacity is roughly ten times the recommended charging current >which is 45 mA) Finally, they are both made in Mexico. The obvious >choice seems to be Radio Shack. Have I overlooked anything? >-- Dont think so. I investigated this a couple of years ago, and came to the conclusion they were all coming out of the same factory, and were identical, I bought some Radio Shaft, then additional GE's (they were on *very* good special, with a charger thrown in). One thing to watch however, is 'D' cells. Both the (consumer retail variety) GE and Radio Shaft products are again identical, but have the same milli-amp-hour rating as the 'C' cells! If you open one up, it is only about 1/3 full of "electrolyte" (probably the wrong term for the contents of a Ni-Cad). They both feel about the same weight. Much higher capacities can be found in GE's catalogue, at much higher $$$'s. BTW folks, a caveat since Ni-Cads are being hyped at the moment: You have no guarantee that Ni-Cads will work satisfactorily in any given piece of equipment unless they are specifically mentioned in the "user-manual". This is due to the fact that a Ni-Cad has a fully charged voltage of ~1.25 (~1.22v during 90%+ of its discharge cycle), while carbon-zink, and alkalines are closer to 1.5volts (which does though decay during use). In particular, "Walkman" type cassette players (no specific brand implied) often are problematic. 9volt battery applications show the problem up worst (a Ni-Cad "9volt" is actually ~7.3volt). Ni-Cads also do not have nearly the same capacity as alkalines (e.g. less time per Ni-Cad charge, than from an alkaline cell in a given piece of equipment). Modern Ni-Cads can however supply much higher currents than other cell types (an ordinary 'AA' Ni-Cad can supply >10amps for short periods - they get *hot*). In addition, for ecology worriers, cadmium is a serious heavy-metal pollutant (Ni-Cad's are banned in some European countries). For the technically minded (sorry, just press 'n' if I'm going on too much, I know a little about Ni-Cads 'cos I fly model Radio Control, the batteries are a weak link): There are two things to watch out for when using Ni-Cads: 1) Discharge Memory. For some strange reason, if you *repeatedly* discharge a Ni-Cad by say 20%, then fully re-charge it, it "remembers" this, and when you now try to discharge it by more than 20%, it wont (actually it will - wow - contradiction within 5 words! - eventually, at the low almost discharged voltage). You should thus nearly fully discharge them before re-charging (but see below). As an example of what is bad, the Ni-Cads in an electric shaver will appear dead fairly soon if you just shave for 5-minutes every day, then shove it back in the charger. (I almost fully discharge mine every couple of weeks, and still get over 45mins of use when travelling after 7 years on the same cells). The memory can even show if you leave the cells *fully charged* for long periods. A rechargable calculator should not be left plugged in - use it off-line until it is just discharged, then re-charge it over-night. For serious applications (i.e. radio control), the cells are continuously cycled when not in use (or at least several times immediately before use), from fully charged to almost discharged. 2) Deep Discharge and Reversed polarity. Unfortunately, the capacities of Ni-Cads vary cell to cell, and when used together, e.g. in a 9volt pack, or 4 AA's together, one of the cells will become discharged before the others, which continue to supply current. This is forced through the dead cell, and, to cut a long story medium length, horrors, IT DOESN'T LIKE IT (would you?). In short, this cell expires rapidly (pushing-up-the-daisies-type-expire). Even with single cells, leaving the equipment "switched-on" after the cells are discharged, is bad news. The solution is to not *completely* discharge, and to match your cells, but that is another story more suitable for net.consumers.tech (as if the above wasn't)! If anyone is interested out there, I can also give some info on "fast-charge" types & etc. Ray Dunn. ..philabs!micomvax!othervax!ray